Polydiethylsiloxanes (diethicones) reportedly are the first series of hybrid silicone polymers with other than methyl substitution, says Gelest Inc. Analogous in structure to dimethicones, diethicones allow the manufacture of a wide range of fluid viscosities. Their beneficial properties include excellent spreading, gas permeability and waterproofness. The company's Sibrid DE 15 (diethicone 50cs) reportedly combines the slip of silicones with organic compatibility to give a smooth, glide-on application.